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Two approaches to the concept of chemical species: Relations between potential energy and molecular shape
Author(s) -
Arteca Gustavo A.,
Mezey Paul G.
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560360834
Subject(s) - van der waals force , curvature , maxima and minima , potential energy , invariant (physics) , chemistry , function (biology) , representation (politics) , conformational isomerism , simple (philosophy) , molecular dynamics , work (physics) , computational chemistry , physics , chemical physics , classical mechanics , statistical physics , molecule , quantum mechanics , geometry , mathematics , mathematical analysis , evolutionary biology , politics , political science , law , biology , philosophy , epistemology
Chemical species are usually defined in terms of the potential energy function. In this work we explore the relationships between this definition and an alternative one, based on the concept of molecular shape. The molecular shape is given a quantitative expression in the framework of the shape group method. The model representation chosen for the molecular surfaces is the continua of fused‐sphere van der Waals surfaces. Simple molecular systems are considered, where the “chemical species” are represented by 1‐dimensional potentials as torsional rotamers. It is shown that within well‐defined ranges of atomic van der Waals radii and nuclear geometries, the identity of the molecular species, as defined by shape, remains invariant under torsional motions. The number and size of such invariance domains can, under certain conditions, follow closely the regions in configuration space where a rotamer is defined according to the minima and curvature of the potential energy function. These findings provide new tools for the study of the interplay between molecular shape and electronic energy, regarding the recognition of active conformations.